Ovarian cancer begins with a tumor in either or both of the ovaries. The type of tumor is determined by the kind of ovarian cell in which it occurs.
Germ cell tumors occur in the germ cells, which produce the eggs. Stromal tumors begin in the stromal cells, which produce most female hormones including estrogen and progesterone. Epithelial tumors occur in epithelial cells, as are found in the layer of tissue covering the ovary, known as the epithelium.
The tumor may be benign or non-cancerous, in which case it may be treated by surgical removal of the whole or part of the ovary. Benign tumors do not spread beyond the ovary. The tumor, however, may be malignant or cancerous, in which case it may spread to other parts of the body.
Most ovarian cancers are of epithelial origin. Because epithelial cancers develop in the surface of the ovary, they have a tendency to spread into other parts of the abdomen. Cancer cells can break off from the tumor, implant themselves in the abdominal cavity or the fatty tissues covering the intestines, and grow. They can also move to the lymph nodes clustered around the aorta.
Epithelial ovarian carcinomas account for roughly 85% of all ovarian cancers, making it the commonest type of this disease. Four subtypes of epithelial ovarian carcinomas—clear cell, serous, mucinous, and endometriod—grow differently, but are treated in the same manner. There is also the undifferentiated type, which grows and spreads more rapidly than the other four.
Transitional cell cancer is another type of ovarian cancer that is treated in a similar manner to epithelial cancer.
Low malignant potential (LMP) tumors, on the other hand, may also develop in the ovaries. They are otherwise known as borderline epithelial ovarian cancers, since even under examination by microscope, they do not appear clearly cancerous. LMP tumors usually occur among women who are younger than the high-risk age group. They are less life threatening than most ovarian cancers. They may cause death, but such cases are rare. Moreover, fatalities from this type of tumor usually occur many years after diagnosis.
Unlike typical ovarian cancers, LMP tumors do not invade stromal cells, nor do they invade the abdomen’s lining tissue should they spread beyond the ovary. LMP tumors are treated differently than epithelial ovarian carcinomas.
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Reviewed by:
Jiade J. Lu, M.D.
Diplomate, American Board of Radiology (Radiation Oncology)
Medical Director
The Cancer Information Network
Date Modified: 06/14/04
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